1. Field of the Invention
The present invention relates to needle forming devices. More particularly, the invention relates to a multistation needle forming device for flat pressing, curving and side pressing one needle blank, or a multiplicity of needle blanks, to form curved rectangular bodied needles. The device is capable of transferring the blanks from one die station directly to the next die station.
2. Description of the Related Art
The production of needles involves many processes and different types of machinery in order to prepare quality needles from raw stock. These varying processes and machinery become more critical in the preparation of surgical needles where the environment of intended use is in humans or animals. Some of the processes involved in the production of surgical grade needles include: straightening spooled wire stock, cutting needle blanks from raw stock, tapering or grinding points on one end of the blank, providing a bore for receiving suture thread at the other end of the blank, imparting flat surfaces on opposite sides of the blank by flat pressing a portion of the needle blank to facilitate grasping by surgical instrumentation and curving the needle where curved needles are desired. Additional processing may be done to impart flat surfaces substantially perpendicular to the flat pressed portions of the needle blank by side pressing a portion of the needle blank to further facilitate grasping by surgical instrumentation and insertion into humans or animals.
Conventional needle processing is, in large part, a labor intensive operation requiring highly skilled workmen. Generally, extreme care must be taken to ensure that only the intended working of the needle is performed and the other parts of the needle remain undisturbed.
Curved rectangular bodied needles have advantages over other needle configurations in many surgical procedures for a variety of reasons including, uniformity of entry depth for multiple sutures and proper "bite" of tissue surrounding the incision or wound. When providing curved rectangular bodied needles for surgical procedures it is desirable for the needles to have a specified rectangular cross-section and a specified curvature, i.e., a predetermined radius of curvature. The desired cross-section and radius of curvature for the finished needle varies with specific applications.
Known methods of forming curved rectangular bodied needles require several separate and distinct operations on various machinery. The needle blank must first be flat pressed to impart initial flat surfaces along barrel portions of the needle blanks located between a tapered point end of the blank and a drilled end. After flat pressing, the needle blank can then be taken from the flat press dies to a curving machine to impart the proper curvature to the needle blank. Care must be taken when removing the blanks from the flat press dies and positioning the needle blank in the curving machinery to avoid disturbing the flat surfaces imparted by the flat pressing operation.
After curving, the flat pressed and curved needle blanks can then be taken from the curving anvil to a side press station to impart flat surfaces substantially perpendicular to the flat pressed sides to give the final rectangular cross sectional profile to the needle barrel. Again care must be taken during removal of the needle blanks from the curving anvil and during side pressing so as to avoid disturbing the previously imparted flat pressed and curved portions of the needle blank.
Known flat pressing techniques create the flat edges on the needle barrel by pressing the barrel portion of the needle blank between a pair of opposing needle dies having the desired length and width characteristics. Typically, the needle blanks are inserted into a lower die and compressed between the dies to impart the flat surfaces on opposed sides of the needle barrels The flat pressed blanks can then be removed from the dies and taken to the curving machinery. After removal of the needle blanks, the dies can also be inspected to ensure no needle blanks remain stuck to one of the dies.
Known needle curving techniques create the curve by bending the needle blank around an anvil structure having a desired curvature. To attain the desired needle configuration, the anvil structure provides a shaping surface for deforming the needle. Typically, the needle is positioned for curving by manually placing the needle for engagement with the anvil structure and holding it in place by a holding device. The needle is subsequently bent by manipulating the holding device so the needle curvature is formed about the shaping surface of the anvil structure. Needles improperly positioned on the anvil may result in a deformation of the previously imparted flat press sides and may have to be reprocessed or discarded.
When needles are made of steel or similar resilient materials, the anvil or mandrel used should have a smaller radius than the radius desired in the final needle. This configuration allows for some springback after the bending operation and ensures that the desired radius of curvature is attained. A disclosure of such features may be found in, for example, U.S. Pat. No. 4,534,771 to McGregor et al.
After flat pressing and curving the needle blank it may be desirable to side press the barrel portion of the needle blank to obtain a rectangular cross-section in the needle barrel. As with the above flat press process, known side pressing techniques require inserting the blank between a pair of dies to compress and impart flat sides to the needle blank. Needles improperly positioned within the dies may become deformed and also have to be discarded or reprocessed.
One disadvantage to conventional needle forming techniques is that typically only one needle processing operation at a time, such as, for example, flat pressing between a pair of dies, curving around an anvil structure or side pressing between another set of dies, can be performed on a single piece of machinery. A further disadvantage is the long processing time and high costs required in forming and transporting the needles between the various machinery. Lastly, a still further disadvantage is the need to readjust several pieces of machinery to process needles of varying lengths and diameters thereby further increasing production time and costs.
Therefore, a need exists for a single needle forming apparatus that is capable of flat pressing, curving, and side pressing a multiplicity of needle blanks or a single needle blank by transporting the needle blanks directly between the various die sets of the same apparatus. It is also desirable to provide a needle forming device which cooperates with a needle feeding fixture for sequentially loading and positioning one or more needles at a first processing station so as to increase the production rate of the needle manufacturing process by maintaining a continuous flow of needle blanks through the device.